EXAFS and XRD studies in synthetic Ni-fluorohectorite

Abstract

In the present work the synthetic clay mineral fluorohectorite was studied by means of an extended X-ray absorption fine structure (EXAFS) in a powder sample with the intention to observe the number of neighboring atoms to the Ni interlayer cation. In addition X-ray diffraction (XRD) was performed in order to follow the hydration states of Ni-fluorohectorite in terms of basal-spacing measurements. The sample conditions were the same for both types of experiments. The EXAFS results show that Ni2+ forms a brucite-like structure in the form of Ni(OH)2, and that this structure coexists with the clay mineral particles. This shows that the Ni atom observed by means of our EXAFS measurements is predominantly the Ni which composes the brucite-like structure and not the interlayer Ni2+ cation. In order to confirm the formation of the brucite-like structure, the EXAFS data from Ni-fluorohectorite were compared to Ni-salt water solutions at various pH.